Telephone receiver



Sept. 7 1926.

ATTORNEY Patented Sept. 7, 1926.

BERTRAND L. HOFFMAN, OF BROOKLYN, EW YORK.

TELEPHONE RECEEVER.

Application filed September 13, 1922. Serial No. 587,968.

This invention relates to a telephone receiver. its object is the production i a receiver, by means of which the air gap between the pole pieces and the diaphragm thereof can be easily varied, to vary the reluctance of the magnetic path of the receiver. A second object or the invention is the said air gap can be easily varied without the use of complicated tools or expert knowledge. A third object is the production of an adjustable receiver which is useful for radio apparatus, wireless telephones and wireless telegraphs. Other objects will be evident from the description, claim and drawings herewith.

It is well known in the art that the distance between the diaphragm and magnet poles of a telephone receiver must be correctly adjusted, so that the reluctance of the magnetic path from pole to pole will be such, as to give the best results. It is usual in the manufacture of telephone receivers to determine by experiment or otherwise some definite fixed value for said distance, and then construct the parts of the receiver, so that when they are assembled this predeter mined distance between the diapl ragm and the pole pieces will be maintained. It is cs- 30 sential to be enabled to vary this distance and thereby provide for variations in the electromagnetic circuit of each individual receiver which may develop either at the time of manufacture due to the material used, or in the methods of magnetizing, or later when the receiver is actually being used for converting electric energy intomechanical vibrations to produce sound.

In the accompanying drawings Fig. 1 represents an enlarged partial section as on the line 1-1 of Fig. 2 of the improved telephone receiver, Fig. 2 shows a top plan view of the receiver with the ear piece removed and Fig. 3 indicates an elevation of the receiver with a modification.

An outer cylindrical shell is provided at .its top end with the exterior thread 21 and at its lower end with the interior thread 22. A supporting disc 25 with the thread 26 on its periphery engages the thread 22 of the shell 20. Angle shaped pole pieces are indicated with the vertical members 28 and the horizontal members 29. Each of the latter has a bifurcated end 30. Eelectric magnetic coils 31 and 32 are wound around the members 28 in the usual manner. Caps production of a receiver, wherein the 33 and bottom supports 34, of nonmagnetic material are provided for the coils. The supports 34 bear upon the members 29 of the pole pieces. Sleeves 35 0t nonmagnetic material are provided for the coils 31 and 32.

Bolts 40 with the nuts 41 at their upper ends and the nuts 42 at their lower ends extend through the supporting disc 25, and clamp the members 29 of the pole pieces the etc. The nuts 42 with said bolts constitute binding posts for the wires 48, that provide electric current for the coils 31 and 32. Pairs of annular shaped permanent magnets 46 are disposed with their ends 47 over the bifurcated ends 30 of the said pole pieces. Clamps 48 of nonmagnetic material bear upon the ends of the top most magnets 46. Screws 50 extend through the supporting disc 25, the openings in the memhere 29 of the pole pieces and are in threaded engagement with the said clamps 48. By means of said clamps 48 and screws 50, the said permanent magnets and the mem bers 29 of the pole pieces are clamped in place.

A. wire 52 extends from one of the bolts 40 to the coil 31 and a wire 53 extends from the other bolt 40 to the coil 32. A wire 54 connects the two coils.

The ear piece of the receiver is provided with the usual opening 61 and the internal thread 62. A. shoulder 63 is also formed with the ear piece. The diaphragm 65 is located upon the top edge of the shell 20 and the shoulder 63 of the ear piece 60 bears thereon.

To adjust the air gap between the ends of the members 28 of the pole pieces and the diaphragm 65, the supporting disc 25 is turned to proper position, and thereby the reluctance of the magnetic path from pole to pole is varied.

In Fig. 8 the receiver is modified by substituting for the shell 20 a shell 70, which has an external thread not shown at its top end similar to 21 for the ear piece 60, but at its bottom end is provided with the external thread 72. The supporting disc 73 is similar to 25 but has formed therewith the flange 74 with the internal threads 75, that engage the threads 72; The nuts 42 are shown with the wires 48 as already explained. The air gap in the modification is varied by turning the supporting disc 73 as explained for the supporting disc 25.

Various modifications may be made in the invention, and the present exemplification is to be taken as illustrative and not limitative thereof.

Having described my invention what I desire to secure by Letters Patent and claim In a telephone receiver thecombination of an outer cylindrical shell with an exterior thread at its top end and an interior thread at its bottom end, a supporting disc with a thread on its periphery in threaded engagement with the interior thread of the shell, a pair of electromagnets each with an angle shaped pole piece having a vertical member and a bifurcated horizontal memher, the said horizontal members bearing on said supporting disc, bolts extending through the supporting disc and the open- 1 ings in the horizontal members of the pole pieces to clamp the latter to said disc, nuts on the lower ends of said bolts, wires for the electric current clamped by said nuts, pairs of annular shaped permanent magnets with their ends over the bifurcated members of the pole pieces, clamps bearing on the ends or" the top most permanent. magnets, bolts connecting said clamps and the supporting disc, to hold said magnets, a diaphragm supported upon the top edge of said cylindrical shell and an ear piece bearing upon the periphery of said diaphragm and in threaded engagement with the threads at the upper end of the shell.

Signed at the borough of Manhattanc city of New York in the county of New York and State of New York, this 12th day of September, A. D. 1922;

' BERTRAND L. HOFFMAN. 

